Electroconvulsive therapy remains an important treatment for severely depressed patients who do not respond adequately to, or are intolerant of, antidepressant medication. As the prevalence of major depression increases, particularly in the geriatric population, the need for effective treatments is an urgent public health concern. Despite refinements in technique, the cognitive impairment associated with ECT remains a serious concern for many patients. Traditionally, ECT has been administered with one of two standard techniques: 1) bilateral (bitemporal) electrode placement or 2) right unilateral electrode placement. Bilateral electrode placement has greater efficacy but causes more cognitive impairment, while right unilateral electrode placement is less effective for some patients but causes less cognitive impairment. Recently, two innovative techniques have shown promise in preliminary studies: 1) right unilateral ECT administered at much higher electrical dose, which may achieve efficacy equivalent to bilateral ECT and 2) a novel electrode placement (bifrontal) which may combine the beneficial properties of both bilateral and unilateral ECT. We propose a double blind, randomized, controlled clinical trial comparing the standard technique of bilateral ECT with two novel techniques - high-dose unilateral ECT and bifrontal ECT. The primary aims of the study are to compare the three treatments in terms of 1) antidepressant efficacy and 2) cognitive effects during and at the end of the treatment course, and over a two-month naturalistic follow-up period. An additional aim is to compare the treatments in terms of quality of life over two months. In this study, 360 patients with major depression are randomized over 4 years at 4 sites. Assessments are the Hamilton Rating Scale for Depression (HRSD), a comprehensive neuropsychological test battery, and quality of life outcome measures. Provisions are made for assuring the ongoing quality of treatments and assessments. The investigators are experienced ECT providers and researchers who are now successfully collaborating on an ongoing NIMH-funded trial of continuation ECT vs. pharmacotherapy (MH55489, MH55486, MH55484). The proposed study will be the first direct comparison of the three types of ECT and will inform psychiatrists about the optimal technique of ECT. The results of this study will promote more effective and safer treatment of the most severely ill depressed patients.